Such a revolving door is known in many kinds of embodiments. The lock used with such revolving doors serves to allow the door wings, after the lock is placed in the unlocked position, to be swivelled aside to provide a spacious escape route. However, during normal use the door wings must be securable in their radial position so that the door can be used as revolving door in its many applications.
U.S. Pat. No. 4,562,665 teaches a magnetic door breakaway system for remote unlocking of doors and apertures. An electromagnet and armature are mounted within a doorframe. Within either the magnet or the armature are depressions and corresponding projections in the other. The document teaches that the armature is preferably movably affixed to the top of the doorframe and by energizing the electromagnet, the projections mate with the depressions make movement of the doorwing impossible. In an emergency situation, the magnet is de-energized and the doorwing may open freely.
From U.S. Pat. No. 4,970,825 a revolving door is known having a plurality of door leaves extending radially outwardly from a center shaft in angularly spaced positions. The door includes upper and lower collapsing mechanisms which are adapted to normally maintain the door leaves in their radial positions, but permit pivotal movement of each door leaf to a collapsed position in the event that the door leaf is subjected to abnormal forces. This document teaches to apply a locking assembly with an electromagnet, which normally is operated to prevent the collapsing mechanism from functioning, so that the door leaves can be collapsed. In the event of an emergency situation, the locking assembly is quickly rendered inoperable by de-energizing the electromagnet, which permits then pivotal movement of the door leaves to their collapsed positions.